Cleaning process and cleaning composition



3,535,160 CLEANING PROCESS AND CLEANING COMPOSITIQN Andrew Arger, 348 Fort Washington Ave., New York, N.Y. 10033 No Drawing. Filed Nov. 14, 1966, Ser. No. 593,693 Int. Cl. B08b 9/08 US. Cl. 134-22 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process for the cleaning of ship double bottoms and a cleaning composition therefor.

Oceangoing vessels are fitted with double bottoms for the storage of fuel oil within the tanks formed by the double bottoms. As the fuel oil is used up, the double bottom tanks are often filled with sea water for ballast. In most cases various grades of bunker oil is used as the fuel, which is a very viscous material. Bunker oil has a tendency to form sludge deposits which impair the burning qualities of the oil. The oil contains petroleum molecules which tend to polymerize and agglomerate, especially in the catalytic presence of iron. Sludge formation is aggravated by oxidation by air, especially in the presence of small amounts of water and of iron. In order to reduce the viscosity of the bunker oil for pumping, double bottoms are most generally equipped with heating coils. Outside of sludge deposits double bottom tanks are also saturated with potentially explosive gases. The accumulated sludge has to be removed and the accumulated gases have to be vented from time to time, but in every case before access could be gained to the tanks for periodic and mandatory survey, repairs, and overhaul.

In the prior art double bottom tanks are cleaned by highly dilute aqueous emulsions of a petroleum solvent. The concentrated cleaning solution of the prior art usually contains 1040% by weight of an emulsifier, with the balance being petroleum solvent. Cleaning is usually carried out at sea utilizing the rocking motion of the ship causing a sloshing around and agitation of the solution in the partially filled double bottom tanks. Cleaning is usually carried out at high sea beyond a certain distance from shore, where the washing solutions can be pumped overboard. A number of cleaning solutions are known in the prior art, which utilize various petroleum solvents, emulsifiers, in various proportions and dilutions, however, none of the prior art cleaning compositions and processes employing them are satisfactory, because the resulting cleaning efliciency is low and the cleaning ability of the prior art cleaning compositions is unpredictable.

It is an object of the present invention to provide an improved method and cleaning composition for the cleaning of double bottom tanks with greater efficiency than the methods and compositions of the prior art.

As used throughout the specification and the claims, the terms double bottom and double bottom tank are intended to include tanks containing residue from a hydrocarbon such as fuels or lubricants, and which tanks are not readily accessible to maintenance personnel for conveniently cleaning from the inside. Consequently, for purposes of the present application, most so-called deep tanks are also intended to be included within the meaning of the aforementioned terms. The word water as used throughout the specification and the claims is intended to include 3,535,16, Patented Oct. 20, 1970 both salt water as well as fresh water, because, all of these waters can be satisfactorily used in accordance with the present invention.

The invention relates to a process for cleaning a double bottom tank of a ship, which comprises the steps of (a) filling the drained tank with water to at least 10% of its capacity; (b) adding to the tank 0.01 to 5% by Weight of the water in the tank of a solution consisting essentially of 1090% by wegiht, based on the solution, of a petroleum solvent, 585% of a chlorinated hydrocarbon having 1-6 carbon atoms in the molecule, and 5-50% by weight of an organic emulsifier; (c) agitating the contents of the tank for an effective cleaning time; (d) emptying the tank; (e) rinsing the tank with water, or aerating the tank, or both.

In accordance with a preferred embodiment of the invention the process comprises (a) filling the drained tank to less than of its capacity; (b) adding to the tank 01 to 2% by weight, based on the water in the tank, of the cleaning composition of the present invention; (c) agitating the contents of the tank for a period between 6 hours and hours; (d) emptying the tank; repeating steps (a), (b), (c), and (d); and (e) rinsing the tank with water or aerating it, or both.

For maximum cleaning efficiency, in accordance with a more preferred embodiment of the process, the empty double bottom tank is filled with water sufficiently to cover the heating coils such as to less than 50% of its capacity, such as through the ballast system, a fire hose, or through the sounding pipe; maintaining high heat on the steam coils to heat the water to a temperature between 40 F. and F., preferably 100-140 F. 9-12 gallons, preferably about 12 gallons of cleaning concentrate per hundred barrels (4200 gallons) tank capacity, is added to the tank through a direct access opening, sounding pipe, or vent lines. This solution is left in the tank from 6 to 96 hours, preferably about 48 hours, while the vessel is subjected to rolling motion of the sea, whereby the solution in the tank is agitated. Subsequently the tank is filled with further amounts of water to less than 75 of its capacity, and is left for a period of /2 a day to 3 days, preferably about 1 day, being subject to further sea roll agitation, heat being maintained throughout. Thereafter the heating system is secured (shut off), the tank is stripped (emptied), preferably while the ship is at high sea to permit pumping overboard the contents of the tank; subsequently, in a second stage of the process, the tank is filled again to about 50% of its capacity with water. The heating system is restarted and 58 gallons, preferably about 8 gallons of cleaning solution is added to the tank per hundred barrel tank capacity. After the cleaning solution is added, the sounding line and/ or vent line is flushed with water to rinse the remaining cleaning solution into the tank, as well as to clean these lines. The solution is maintained, while heating, in the tank for another 6-96 hours, preferably about 48 hours while subject to the natural roll of the ship. Then the tank is filled to capacity, the heating system is secured, then the tank is completely stripped, rinsed by refilling, and is then restripped.

The cleaning composition of the invention comprises 1090% by weight, based on the solution, of a petroleum solvent, 5-85% by weight of a chlorinated hydrocarbon having 1-6 carbon atoms in the molecule, and 550% by weight of an emulsifier. This cleaning composition is an advance over the prior art double ibottom tank cleaner compositions, because substitution of part of the petroleum solvent in the prior art two-component systems, 'with a chlorinated hydrocarbon solvent of the type specified, results in greater cleaning efficiency and predictability of operation. Chlorinated hydrocarbon solvents have not been used in the prior art in the cleaning of double bottom tanks, in fact, various admonitions in the literature 3 have tended to advise against their use in aqueous systems. Chlorinated hydrocarbon solvents tend to hydrolyze in the presence of water and form corrosive acids. This is to be avoided when in use in contact with the metallic hulls of ships.

It is a feature of the present invention, whereby I have discovered that substitution of a chlorinated hydrocarbon for part of the petroleum solvents in the prior art double bottom cleaners results in a synergistic increase in the cleaning power of the solution. In the cleaning of double bottoms where the cleaning compositions of the present invention are used in a high degree of dilution, two competing phenomena take place: (a) the cleaning and sludge-dissolving action of the dilute, aqueous cleaning solution; and (b) hydrolysis of the chlorinated hydrocarbon solvent resulting in the formation of corrosive acids. I have discovered that at dilutions whereby the cleaning solution of the invention is present in a concentration of only between 0.01 and 5% by weight based on the aqueous solution, the first phenomenon progresses at a much greater rate than the second phenomenon, consequently complete cleaning can be conveniently accomplished well before any noticeable corrosion will occur. In other words, the dwell time of dilute cleaner in the tank necessary for complete cleaning, is much shorter than the dwell time which would result in damaging corrosion. Accordingly, in 0.01-5% by weight dilution range, and within the time periods required for effective cleaning, the corrosion effect is negligible, mostly not even perceptible. The aforementioned factors make the cleaning compositions of the invention suitable in such application as the cleaning of double bottom tanks where large dilutions are employed.

The cleaning compositions of the invention contain -90% by weight, preferably 60-90% by weight of a petroleum solvent which can be aromatic, parafiinic or a naphthenic hydrocarbon solvent. The aromatic petroleum solvents which can be employed in the compositions of the invention have a boiling point between 100 C. and 300 C., the aliphatic and the naphthenic solvents which can be used have boiling points between 95 C. and 275 C. Although both paraffinic and olefinic solvents can be used, the latter are expensive and less preferred. Generally aromatic petroleum solvents or mixtures of petroleum solvents wherein the aromatics predominate, are preferred, because the aromatics can be most easily emulsified.

The chlorinated hydrocarbon containing between 1 and 6 carbon atoms is employed in a concentration of 5-85% by weight, preferably 520% by weight of the solution, and is a straight chain, aliphatic or cyclic compound .In the following some examples are given of chlorinated hydrocarbons useful in the compositions of the present invention. Useful aliphatic chlorinated hydrocarbons include 1,1,1-trichloroethane, methylene dichloride, perchloroethylene, and carbon tetrachloride. The latter is somewhat less preferred because of the toxicity of its fumes. Examples of aromatic chlorinated hydrocarbons include dichlorobenzenes, with o-dichlorobenzene being preferred.

The organic emulsifier is employed in a concentration of 5-50% by weight, preferably 5-25% by weight, based on the cleaning solution. While I am not aware of any organic emulsifier which could not be used in the composition of the invention, nonionic organic emulsifiers are preferred, because these have good salt water stability and are most effective at operating temperatures. Most preferred nonionic organic emulsifiers are alkylphenols condensed with ethylene oxide, in which the alkyl group contains 6-12 carbon atoms, and the degree of ethoxylation is 6-15 mols. Other emulsifiers include alkyl amine salts of alkylbenzene sulfonates where the alkyl amine carbon chain contains between 3 and 6 carbon atoms and the alkyl chain of the sulfonate contains 10-15 carbon atoms; diethanolamide condensates of fatty acids, where the alkyl chain of the fatty acid contains between 10 and 20 carbon atoms, for instance, oleyldiethanolamide; ethoxylated alcohols, where the alkyl chain contains 1-18 carbon atoms and the degree of ethoxylation varies between 6-20 mols ethylene oxide; petroleum sulfonates, having a molecular weight of 400-500; fatty acid esters of polyethylene glycol, wherein the fatty acid contains between 10 and 29 carbon atoms and the molecular weight of the polyethylene glycol is 300-600; fatty acid esters of polyhydric alcohols and 4-20 mols ethylene oxide, Where the fatty acid contains between 10 and 18 carbon atoms, and the polyol contains 3-6 carbon atoms and 3-6 hydroxy groups; and fatty acid condensates of ethylene oxide, wherein the fatty acid contains 10-29 carbon atoms and the degree of ethoxylation is 5-30 mols; phosphorylated ethoxylated alcohols, or phosphorylated ethoxylated alkyl phenols, wherein the degree of phosphorylation can be 1 mol P 0 per 3 mols of the phosphorylated compound. Commercial examples of the aforementioned types of emulsifiers include the alkyl amine salt sold under the trade name Emcol P-10-59; an ethoxylated alcohol sold under the trade name JN-70; a petroleum sulfonate sold under the trade name Petronate L; a fatty acid ester sold under the trade name PEG-400; and fatty acid condensates sold under the trade designation Lipal 15-T, and Lipal 58, both; a phosphorylated ethoxylated alkyl phenol sold under the trade name GAFAC-RE-6 10.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the compositions possessing the features, properties, and the relation of elements, which are exemplified in the following detailed disclosure.

EXAMPLE The double bottom tank of a freighter is drained, leaving in the tank only the heavy sludge deposit from the bunker fuel oil stored in the tank. The tank is filled with water through the ballast system, up to and covering the heating coils, while maximum heat is contributed by the coils. A cleaning solution is prepared containing by weight of an aromatic petroleum hydrocarbon sold by the Standard Oil Corp. (New Jersey) under the trademark Esso Han, 10% by weight of 1,1,1-trichloroethane, and 10% by weight of branched chain nonyl phenol condensed with 9 mols of ethylene oxide. Twelve gallons of this cleaning solution per hundred barrels of tank capacity is added to the tank through the sounding pipe. The solution is left in the tank for about 48 hours while the ship is at high sea and subject to the rolling wave motion which agitates the solution in the partly filled tank. Thereafter the tank is filled with further amounts of water to about 75% of its capacity. This solution is subjected to the rolling motion of the sea for about one day, heat being maintained throughout. The heating system is subsequently secured, the tank is stripped by pumping the contents thereof overboard. In a second stage of the process the tank is filled to about 50% of its capacity with the steam coil heating system being in operation, and about 8 gallons of the cleaning solution is added to the tank per hundred barrel tank capacity, through a service opening in the tank. The solution is allowed to remain in the tank for about 48 hours while it is subjected to the rolling motion of the sea, then the tank is filled to capacity, the heating system is secured, stripped, and rinsed by refilling and restripping. The tank, upon inspection, is found to be completely clean and gas-free.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Process for cleaning oil storage tanks of ships, which comprises the steps of (a) filling a drained oil storage tank with water to at least 10% of its capacity; (b) adding to the tank 0.01-5% by weight based on the Weight of the water added to the tank of a solution consisting essentially of 10-90% by weight, of a petroleum solvent, 5-85% by weight of a chlorinated hydrocarbon having 16 carbon atoms in the molecule, and 55 by weight of an organic anionic or nonionic emulsifier; (c) agitating the contents of the tank for an effective cleaning time; (d) emptying the tank; (e) rinsing the tank with water, or aerating the tank, or both.

2. A process for cleaning oil storage tanks of ships, which comprises the steps of (a) filling the drained oil storage tank with water to about 10% to 50% of its capacity; (b) adding to the tank 9-12 gallons per hundred barrels of tank capacity of a cleaning solution consisting essentially of 10-90% by Weight, based on the solution, of a petroleum solvent, -85 by Weight of a chlorinated hydrocarbon having 1-6 carbon atoms, and 5-50% by weight of an organic anionic or nonionic emulsifier; (c) agitating the contents of the tank for about 6-96 hours; ((1) adding further amounts of water to fill the tank up to 75% of its capacity; (e) maintaining the contents of the tank in the tank for /2 day to 3 days; (f) stripping the tank; (g) filling the tank from about to 75 of its capacity with water; (h) adding to the tank 5-8 gallons of said cleaning solution per hundred barrels of tank capacity; (i) agitating the contents of the tank for 6-96 hours; (j) filling the tank to capacity with water; (k) stripping the tank; (1) refilling the tank with water; and (m) restripping the tank.

3. The process of claim 1 wherein the nonionic organic emulsifier is selected from the group consisting of ethoxyalkylated derivatives of alcohols, alkyl phenols, fatty acids, fatty amines, alkanolamines, alkanolamides and polyhydric fatty acid esters having from 6 to 22 carbon atoms.

4. Process for cleaning oil storage tanks of ships which comprises the steps of (a) filling the drained oil storage tank with water from about 10% to 75 of its capacity; (b) adding to the tank 0.01-5% by weight, based on the weight of the water added to the tank, of a solution consisting essential of 10-90% by weight of a petroleum solvent,

5-85% by Weight of a chlorinated hydrocarbon having 1-6 carbon atoms and 550% by weight of an organic anionic or nonionic emulsifier; (c) agitating the contents of the tank for an effective cleaning time; (d) emptying the tank; (e) repeating steps (a), (b), (c) and (d); and (f) rinsing the tank with water or aerating the tank, or both.

5. Process according to claim 13, wherein, after step (a), the water is heated to a temperature of 180 F. and maintained at said temperature during steps (b) and (c).

6. A process according to claim 3, wherein the water is added to the tank in steps (a) and (g) is heated to a temperature of 40180 F., and maintained at said temperature during steps (b), (c), (d), (e), (g), (h) and (i).

7. A process according to claim 3, wherein the nonionic organic emulsifier is selected from the group consisting of ethoxyalkylated derivatives of alcohols, alkyl phenols, fatty acids, fatty amines, alkanolamines, alkanolamides and polyhydric fatty acid esters having from 6 to 22 carbon atoms.

References Cited UNITED STATES PATENTS 1,722,211 7/1929 Guardino 134-40 Re 19,374 11/1934 Butterworth 134--10 2,466,632 4/1949 Borus 252- 2,509,197 5/1950 Borus et al 252170 2,952,571 9/1960 Freedman 134-22 3,167,514 1/1965 Baker 252170 LEON D. ROSDOL, Primary Examiner W. E. SCHULZ, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,535,160 October 20, 1970 Andrew Arger It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 7, "13" should read 4 lines 11 and l6, "3", each occurrence, should read Signed and sealed this 1 th day of February 1971.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

b Commissioner of Patents Attesting Officer 

